1. Field of the Invention
The present invention relates to a method of pattern detection for detecting positions of electronics parts and mounting positions
2. Description of the Prior Art
Various approaches for detecting positions of an object such as an electronics part are known. In template matching methods, a characteristic part of an object is previously obtained as a template, and a whole contour of an image of the object, or an image position of the object, is detected, and then position matching of the detected image of the object is performed with the template. In matched filter techniques, a matched filter is matched to a contour of an image of an object, and the image is scanned by using the filter. Windows are provided inside and outside the matched filter to detect the brightness in the windows, and a position of the image of an object is determined as a position having the largest difference between a sum of the brightness in the inside and the outside windows. In edge detection techniques, a processing area including an object is scanned along a constant direction using a plurality of windows to detect edge points (or boundaries) in each scan where the brightness changes largely, and a position of a contour edge line connecting the detected edge points is determined to be an image position of the object.
However, in the template matching techniques and the matched filter techniques, a template used in the template matching technique and a matched filter used the matched filter technique have the same shape as the image of the object to be recognized. Therefore, if the image of the object is inclined, its position becomes difficult to be detected or has a large detection error. Further, a slope of the image of the object cannot be determined based on the detected image. Then, in order to detect a position of an image of the object, repetitive scanning is performed with the slope of the template or the matched filter gradually changed, and this process takes a long time.
In the edge detection techniques, it is difficult to distinguish a contour of an image of an object to be recognized from point and linear noises. Thus, this technique is prone to be affected by noises, and an erroneous recognition, due to noises, may occur.